The entoptic phenomenon of the observation of one's own leukocytes moving in the macular microcirculation will be used as a non-invasive method: 1) To investigate the blood flow autoregulation process, following a sudden increase of intraocular pressure. The study will be conducted in normal volunteers and in patients with maculopathy secondary to diabetes mellitus. The following parameters of the process will be determined: a) the time lag before the beginning of the autoregulatory response, b) the time required for the response, and c) the change in vascular resistance at maximum autoregulation. 2) To test macular pathology and visual function in patients with ocular diseases secondary to senile macular degeneration, ocular hypertension, glaucoma and diabetes. Relative changes in number, speed and pulsatility of the leukocytes as well as relative and absolute scotomas perceived in the field of particles will be correlated with ocular pathology, visual function and the course of the disease. 3) To evaluate preoperatively macular pathology and potential visual function in eyes with ocular media opacities such as cataracts, anterior chamber and vitreous hemorrhage secondary to diabetes and trauma. The test results will be correlated with macular pathology and visual outcome after surgery. A technique based on the matching, by the subject, of the movement of his own leukocytes to a computer simulation of this movement will be implemented in order to characterize quantitatively the density and speed of the leukocytes (maximum and minimum speed) in the macular retinal microcirculation.